PLoS One

Quantitative analysis of the vascular network anatomy is critical for the understanding of the vasculature structure and function. In this study, we have combined microcomputed tomography (microCT) and computational analysis to provide quantitative three-dimensional geometrical and topological characterization of the normal kidney vasculature, and to investigate how 2 core genes of the Wnt/planar cell polarity, Frizzled4 and Frizzled6, affect vascular network morphogenesis. Experiments were performed on frizzled4 (Fzd4-/-) and frizzled6 (Fzd6-/-) deleted mice and littermate controls (WT) perfused with a contrast medium after euthanasia and exsanguination. The kidneys were scanned with a high-resolution (16 μm) microCT imaging system, followed by 3D reconstruction of the arterial vasculature. Computational treatment includes decomposition of 3D networks based on Diameter-Defined Strahler Order (DDSO). We have calculated quantitative (i) Global scale parameters, such as the volume of the vasculature and its fractal dimension (ii) Structural parameters depending on the DDSO hierarchical levels such as hierarchical ordering, diameter, length and branching angles of the vessel segments, and (iii) Functional parameters such as estimated resistance to blood flow alongside the vascular tree and average density of terminal arterioles. In normal kidneys, fractal dimension was 2.07±0.11 (n = 7), and was significantly lower in Fzd4-/- (1.71±0.04; n = 4), and Fzd6-/- (1.54±0.09; n = 3) kidneys. The DDSO number was 5 in WT and Fzd4-/-, and only 4 in Fzd6-/-. Scaling characteristics such as diameter and length of vessel segments were altered in mutants, whereas bifurcation angles were not different from WT. Fzd4 and Fzd6 deletion increased vessel resistance, calculated using the Hagen-Poiseuille equation, for each DDSO, and decreased the density and the homogeneity of the distal vessel segments. Our results show that our methodology is suitable for 3D quantitative characterization of vascular networks, and that Fzd4 and Fzd6 genes have a deep patterning effect on arterial vessel morphogenesis that may determine its functional efficiency

Heart Rhythm

BACKGROUND Beyond pulmonary vein (PV) isolation, anatomic isthmus transection is an adjunctive strategy for persistent atrial fibrillation. Data on the durability of multiple lines of block remain scarce.OBJECTIVE The purpose of this study was to evaluate the impact of gaps within such a lesion set.METHODS We followed 291 consecutive patients who underwent (1) vein of Marshall ethanol infusion, (2) PV isolation, and (3) mitral, cavotricuspid, and dome isthmus transection. Dome transec-tion relied on 2 distinct strategies over time: a single roof line with touch-ups applied in case of gap demonstrated by conventional ma-neuvers (first leg), and an alternative floor line if the roof line ex-hibited a gap during high-density mapping with careful electrogram reannotation (second leg).RESULTS Twelve-month sinus rhythm maintenance was 70% after 1 procedure and 94% after 1 or 2 procedures. Event-free survival af-ter the first procedure was lower in case of residual gaps within the lesion set (log-rank, P = .004). Delayed gaps were found in 94% of a second procedure performed in the 69 patients relapsing despite a complete lesion set with PV gaps increasing the risk of recurrence of atrial fibrillation (67% vs 34%; P = .02) and anatomic isthmus gaps supporting a majority of atrial tachycardias (60%). Between the first leg and the second leg, a significant decrease was found in roof lines considered blocked during the first procedure (99% vs 78%; P , .001) and in delayed dome gaps observed during a second procedure (68% vs 43%; P = .05).CONCLUSION Gaps are arrhythmogenic and can be reduced by optimized ablation and assessment of lines of block. Closing these gaps improves sinus rhythm maintenance

Bifurcation angle distribution.

<p>A & B: Bifurcation angles (<i>Θ</i>) for individual groups for the whole organ (A) and their frequency distribution (B). C: Average angles per DDSO. In the box chart diagrams in A, the boxes determinate the interval within the 25th and 75th percentiles and whiskers denote the interval within the 5th and 95th percentiles, lines within the boxes indicate the medians, and the small squares stand for the average value. The error bars in panel C stand for the SD. Black: WT, blue: <i>Fzd4</i>^<i>-/-</i>, red: <i>Fzd6</i>^<i>-/-</i>.</p

Global structural characteristics of vascular trees.

<p>Total overall length <i>l</i> of the vasculature (A), overall vessel volume <i>V</i> (B) and the fractal dimension <i>D</i>_f (C). Black: WT, blue: Fzd4^-/-, red: Fzd6^-/-. Small dots represent computed values of individual samples in a given phenotype and the crosses signify the corresponding averages. * indicates <i>P</i><0.05 <i>versus</i> WT. § indicates <i>P</i><0.05 Fzd4^-/- <i>versus</i> Fzd6^-/-.</p

Schematic representation of vessel network extraction and classification algorithm.

<p>A: 2D example of an artificial unprocessed vascular segment. Color intensity signifies the HU value of a given voxel. B: Binary image of the vessel after thresholding. Black voxels are foreground voxels, while white voxels characterize the background. C: The application of a morphological closing operator to the binary image. D: Skeletonization of the processed binary image. The skeleton is represented with a thin dotted line. E: Extracted individual centerline points as nodes of a disconnected network. F: Establishing connections between suitable nearest neighbors. G: Connecting close enough nodes with degrees 0 and 1 (red lines, colored segments characterize individual sub-networks). H: Establishing connections between unconnected sub-networks. Light gray nodes and edges signify removed components. I: An illustration of the Strahler classification scheme. The gray nodes have not yet prescribed SO values, whereas other colors of nodes correspond to the SO as given by the color-bar on the right.</p

Diameter and length distribution.

<p>A, B, C. Log-log plots of absolute (A) and relative (B) diameter distributions, and the average diameters in individual Strahler Orders (DDSO) (C). D, E, F. Log-log plots of absolute (D) and relative (E) vessel segment length distribution and average vessel segment lengths of individual Strahler Orders (F) for WT (black), <i>Fzd4</i>^-/-(blue) and <i>Fzd6</i>^-/-(red) phenotypes. Error bars stand for the SD.</p

Morphofunctional characteristics of vascular networks.

<p>Number of vessel segments (A), estimation of vessel resistance <i>R</i>_DDSO (B), shortest distance between terminal elements (C) and its frequency distribution (D) for the three sub-populations. In the box chart diagrams (C) the boxes determinate the interval within the 25th and 75th percentiles and whiskers denote the interval within the 5th and 95th percentiles, lines within the boxes indicate the medians, and the small squares stand for the average value. Black: WT, blue: <i>Fzd4</i>^-/-, red: <i>Fzd6</i>^-/-. The error bars in panels A and B stand for the SD.</p

Electrophysiological study prior to planned pulmonary valve replacement in patients with repaired tetralogy of Fallot

International audienceAIM: Ventricular arrhythmias (VAs) are the most common cause of death in patients with repaired Tetralogy of Fallot (rTOF). However, risk stratifying remains challenging. We examined outcomes following programmed ventricular stimulation (PVS) with or without subsequent ablation in patients with rTOF planned for pulmonary valve replacement (PVR). METHODS: We included all consecutive patients with rTOF referred to our institution from 2010 to 2018 aged ≥18 years for PVR. Right ventricular (RV) voltage maps were acquired and PVS was performed from two different sites at baseline, and if non-inducible under isoproterenol. Catheter and/or surgical ablation was performed when patients were inducible or when slow conduction was present in anatomical isthmuses (AIs). Postablation PVS was undertaken to guide implantable cardioverter-defibrillator (ICD) implantation. RESULTS: Seventy-seven patients (36.2 ± 14.3 years old, 71% male) were included. Eighteen were inducible. In 28 patients (17 inducible, 11 non-inducible but with slow conduction) ablation was performed. Five had catheter ablation, surgical cryoablation in 9, both techniques in 14. ICDs were implanted in five patients. During a follow-up of 74 ± 40 months, no sudden cardiac death occurred. Three patients experienced sustained VAs, all were inducible during the initial EP study. Two of them had an ICD (low ejection fraction for one and important risk factor for arrhythmia for the second). No VAs were reported in the non-inducible group (p < .001). CONCLUSION: Preoperative EPS can help identifying patients with rTOF at risk for VAs, providing an opportunity for targeted ablation and may improve decision-making regarding ICD implantation

Curr Cardiol Rep

PURPOSE OF REVIEW: Imaging plays a crucial role in the therapy of ventricular tachycardia (VT). We offer an overview of the different methods and provide information on their use in a clinical setting. RECENT FINDINGS: The use of imaging in VT has progressed recently. Intracardiac echography facilitates catheter navigation and the targeting of moving intracardiac structures. Integration of pre-procedural CT or MRI allows for targeting the VT substrate, with major expected impact on VT ablation efficacy and efficiency. Advances in computational modeling may further enhance the performance of imaging, giving access to pre-operative simulation of VT. These advances in non-invasive diagnosis are increasingly being coupled with non-invasive approaches for therapy delivery. This review highlights the latest research on the use of imaging in VT procedures. Image-based strategies are progressively shifting from using images as an adjunct tool to electrophysiological techniques, to an integration of imaging as a central element of the treatment strategy.L'Institut de Rythmologie et modélisation Cardiaqu

Pulsed field ablation prevents chronic atrial fibrotic changes and restrictive mechanics after catheter ablation for atrial fibrillation

International audiencePulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation.Cardiac magnetic resonance was performed pre-ablation, acutely (&lt;3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P &lt; 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA.Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions